(a) Field of the Invention
The present invention relates to a small thickness lap-top computer and, more particularly, to a lap-top computer having a reduced thickness by reducing the height of the key switches.
(b) Description of the Related Art
Small-size data processing devices, such as lap-top personal computers including a note type computer and a sub-note type computer and word processors, have become smaller and smaller in the horizontal size thereof as well in the vertical size. In this text, these data processing devices are generically called lap-top computers. A lap-top computer generally has a computer body and a top cover mounting thereon a display unit and attached to the computer body with a hinge for selecting between an open state and a closed state of the top cover.
A user opens the top cover, adjusts the angle of the top cover with respect to the computer body for observing the display unit, then operates to press the key switches on the key-board. The user finally closes the top cover after the operation of the lap-top computer for protection of the key board and the display unit. The top cover generally has a peripheral stripe protrusion extending along the outer periphery of the display unit and protruding therefrom by an amount corresponding to the thickness of the key board including the key switches. When the top cover is closed to the computer body, the protrusion contacts with the outer periphery of the computer body with the key switches on the key board being received in the space formed by the top cover and the computer body and defined by the inner periphery of the peripheral protrusion.
There is a strong demand that the lap-top computer be of a smaller size and a lower weight. It may be considered that the size of the computer body should be reduced together with the key board. This is in fact not practical, however, because the smaller key board having smaller key switches or a smaller space therebetween is difficult to operate. Alternatively, it may be considered that the amount of protrusion of key switches should be reduced by reducing the stroke of the key switches to thereby reduce the overall thickness of the lap-top computer. This is not practical either, because the smaller stroke impairs the feeling of the operation of the key switches. Further, it may be considered that the size of the top cover should be reduced; however, the smaller top cover reduces the size of the display unit, which impairs the observableness of the display unit by the user. After all, it is preferable that the smaller size and the lower weight be achieved by reducing the thickness of the top cover together with the display unit.
Patent Publication JP-A-5-119884 describes a lap-top computer wherein the smaller size and the lower weight of the lap-top computer are achieved while maintaining the stroke of the key switches. In the lap-top computer, each key switch has a key cylinder and a piston driven by compressed air to urge the key switch. The compressed air is supplied from a compressor which operates during an operational mode of the lap-top computer to urge the key switch upward, and stops operation during an idle mode of the lap-top computer to allow the key switches to stay at the bottom for reduction of the amount of protrusion. Thus, the lap-top computer has a smaller height of the peripheral protrusion and yet an enough space for the key switches without contact of the key switches with the surface of the display unit, which is desirable, thereby achieving a smaller size and a lower weight of the lap-top computer.
The lap-top computer described in the publication has a complicated configuration including the compressor, an air chamber for communicating each key cylinder with the compressor, and a valve assembly for switching the compressed air. Thus, the described lap-top computer is expensive and is more likely to suffer from a malfunction due to the provision of the compressor system.
It may be considered that a configuration, wherein the surface of the display unit urges the key switches toward the bottom when the top cover is closed, reduces the overall thickness of the lap-top computer. However, the reactive force of the key switches may generate a warp or deformation of the surface of the display unit, which is undesirable.